The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An environmentally-friendly technology of a vehicle is a core technology which controls survival of a future automobile industry, and advanced car makers have focused their energy on the development of an environmentally-friendly vehicle to comply with environmental and fuel efficiency regulations.
Therefore, car makers have developed an electric vehicle (EV), a hybrid electric vehicle (HEV), a fuel cell electric vehicle (FCEV), and the like, as future vehicle technologies.
Since the future vehicle has various technological restrictions such as a weight and cost, the vehicle makers have paid attention to the hybrid electric vehicle as an alternative of a realistic problem for meeting exhaust gas regulations and improving fuel efficiency performance and have entered into keen competition for commercializing the hybrid electric vehicle.
The hybrid electric vehicle is a vehicle using two or more power sources. Two or more power sources may be combined by various schemes. For example, a gasoline engine or a diesel engine using the existing fossil fuel and a motor/generator driven by electric energy are mixed and used as the power sources.
The hybrid electric vehicle generally uses an engine and a motor/generator, and uses as a secondary power source a motor/generator having a relatively excellent low-speed torque characteristic at a low speed and uses as the primary power source an engine having a relatively excellent high-speed torque characteristic at a high speed.
As a result, the hybrid electric vehicle is excellent in fuel efficiency enhancement and reduction of exhaust gas because an operation of the engine using fossil fuel stops and the motor/generator is used at a low-speed section.
A double clutch transmission (DCT) may be an example of a transmission applicable to such a hybrid electric vehicle. Such a DCT includes two clutches applied to a manual transmission scheme, and thereby enhances efficiency and convenience.
The DCT alternatingly activates odd-numbered shift-stages and even-numbered shift-stages by alternatingly operating two clutches, and thereby improves continuity in torque transmission.
However, we have discovered that the DCT shows relatively high degree of clutch wear and energy loss in starting of a vehicle and rearward slip in starting of a vehicle on a slant. In addition, the DCT is typically controlled with a short shift-control period considering low heat capacity, and thus may easily show a shift shock.
In addition, in order to apply the DCT to a hybrid electric vehicle, an appropriate arrangement of a motor/generator as a power source must be devised.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.